Refactor of sorting/grouping logic

[sircharlo]

This is a playground to eventually simplify and improve the logic of sorting and grouping, and even allow for collapsible groups (such as for referred publications).

Todo

• Refactor day media to allow children in DynamicMediaObject, group based on extractCaption
• Fix lookupPeriod indicate type of item ("dynamic", "watched", "additional")
• Fix lookupPeriod clear to not wipe lookupPeriod, but rather to remove dynamically added items
• Get rid of separate mediaSort object
• Add "initial position" key to be able to reset sort
• Get rid of separate additionalMediaMaps object; fold into lookupPeriod
• Get rid of separate watchedMedia object
• Have all media elements live in one place (lookupPeriod), to allow for intuitive sorting and persisting
• Create new MediaItemOrGroup component, that will be used to display an item or group
• Use something like https://github.com/MaxLeiter/sortablejs-vue3 as a replacement for @formkit/drag-and-drop
• Allow sorting of watched and additional media
• Persist drag-and-drop sorting
• Re-enable Reset Sort button
• Run addDayToExportQueue after sorting
• Restore drag/drop sorting + drop files into window behaviour